JP3161260B2 - Gear transmission - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gear transmission for a vehicle, and more particularly to a gear transmission configured to prevent gear meshing noise and gear rattling noise.

[0002]

2. Description of the Related Art A basic structure of a general manual transmission for a vehicle will be described with reference to FIG. 11 which is described in Japanese Utility Model Publication No. Sho 62-15558. Drive gears 3 and 4 that are spline-fitted and that always mesh with a drive gear that rotates integrally with an input shaft (not shown) are rotatably arranged on both left and right sides of the clutch hub 2. Spline pieces 5 and 6 are spline-fitted to these driven gears 3 and 4 on the clutch hub 2 side. Of these spline pieces 5, 6, tapered cone portions 7, 8 are formed on the outer periphery of the boss portion extending toward the clutch hub 2, and synchronizer rings 9, 10 are formed on the tapered cone portions 7, 8 in the axial direction. It is fitted in a predetermined size and movably. A hub sleeve 11 is engaged with the outer peripheral portion of the clutch hub 2 via a shifting key 13 biased by a key spring 12 so as to be movable only in the axial direction. A chamfer is formed on the outer periphery of each of the synchronizer rings 9 and 10, and splines 14 and 15 for engaging with the hub sleeve 11 are formed on an outer periphery of each of the spline pieces 5 and 6. ing.

In the manual transmission for a vehicle constructed as described above, when the hub sleeve 11 is moved to one of the driven gears 3 and 4, the synchronizer rings 9 and 10 are pushed by the keys. Spline piece 5,
Move to the 6 side. As a result, the synchronizer ring 9,
10 is engaged with the spline pieces 5, 6 by the tapered cone portions 7, 8, and starts to rotate synchronously. Hub sleeve 11
When the hub sleeve 11 is further moved after the chamfer of the synchronizer rings 9 and 10 come into contact with each other, the hub sleeve 11 is moved to the synchronizer rings 9 and 1.
The 0 chamfer is pushed forward and engaged with the splines 14 and 15 of the spline pieces 5 and 6.

The synchronizer rings 9 and 10 act when the hub sleeve 11 is engaged with the spline pieces 5 and 6 on the driven gears 3 and 4 side, and are in a neutral state shown in FIG. In a state where a predetermined gear is set, the synchronizer rings 9 and 10 are stopped or rotated together with the clutch hub 2. On the other hand, the input shaft and the driving gear described above rotate at a different speed while including the rotational fluctuation of the engine, and the driven gears 3 and 4 that can idle on the output shaft 1 are driven gears. And rotate. At this time, a backlash is generated between the driving gear and the driven gears 3 and 4 due to fluctuations in the rotation of the engine, and the teeth are beaten by the amount of the backlash, thereby generating an abnormal noise (toothing noise).

[0005]

Therefore, in a conventional manual transmission for a vehicle, a spring 14 for urging the synchronizer rings 9 and 10 in the axial direction is inserted into the clutch hub 2 and the synchronizer rings 9 and 10 are tapered to a tapered cone portion. The spline pieces 5, 6 (the driven gears 3, 4) are gently pressed against the splines 7 and 8 to apply drag resistance to prevent the generation of the abnormal noise. However, since drag resistance is constantly generated in the tapered cone portions 7 and 8, the life of the synchronizer rings 9 and 10 is shortened, and the operating force and the power loss at the time of gear shifting are increased. In the manual transmission for a vehicle described in Japanese Utility Model Publication No. 62-15558, the spring 14 is made of a shape memory alloy, and the operation of the spring 14 is controlled by the temperature. Similarly, drag resistance was also generated.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to effectively prevent generation of abnormal noise between an output shaft and a driven gear, and to prevent unnecessary drag resistance accompanied by power loss. It is an object of the present invention to provide a gear transmission that can perform the following.

[0007]

In order to achieve the above object, the present invention provides a second rotating member which is dragged by an input shaft with respect to a first rotating member which rotates integrally with an output shaft. Based on the relative rotational speed of the input gear, that is, the magnitude of the rotational speed of the input shaft and the rotational speed of the output shaft, drag resistance is applied to the driven gear to prevent generation of abnormal noise.

More specifically, the invention described in claim 1 is a drive gear that rotates integrally with the input shaft, and a driven gear that is always meshed with the drive gear and is rotatably supported on the output shaft. A clutch hub that rotates integrally with the output shaft, a hub sleeve movably engaged with an outer peripheral portion of the clutch hub in an axial direction, and the hub sleeve moves with the axial movement of the hub sleeve. And a synchronizer ring that applies drag resistance to the driven gear and performs synchronous rotation with the driven gear, wherein a first rotating member that rotates integrally with the output shaft; A second rotating member supported so as to be rotatable relative to the rotating member by a predetermined angle is disposed so as to face the output shaft, and the driven gear and the second rotating member are connected to each other. And a friction transmission unit for transmitting torque by the first rotation member and the first rotation member are operated by rotation of the second rotation member relative to the first rotation member in one predetermined direction. A separating mechanism for separating the second rotating member and the second rotating member from each other in the axial direction is provided between the first rotating member and the second rotating member, and the second rotating member and the synchronizer ring are mounted on the output shaft. , And are arranged facing each other.

According to a second aspect of the present invention, there is provided a driving gear rotating integrally with an input shaft, a driven gear constantly meshed with the driving gear and rotatably supported on an output shaft, and the output shaft. A clutch hub that rotates integrally with the hub, a hub sleeve movably engaged with an outer peripheral portion of the clutch hub in an axial direction, and the hub sleeve and the driven gear as the hub sleeve moves in the axial direction. And a synchronizer ring that applies drag resistance to the output shaft and synchronously rotates the output shaft and a first rotating member that rotates integrally with the output shaft. A second rotating member supported so as to be rotatable relative to a predetermined angle is disposed to face the output shaft, and torque is transmitted between the driven gear and the second rotating member. Friction transmission unit is provided to perform, it is operated by the relative rotation of the predetermined direction of the second rotating member with respect to the first rotary member, these first
A separating mechanism for separating the rotating member and the second rotating member from each other in the axial direction is provided between the first rotating member and the second rotating member, and the second rotating member and the driven gear are provided. Are disposed opposite to each other on the output shaft.

[0010]

According to the above construction, the first rotating member rotates integrally with the output shaft, while the second rotating member rotates while transmitting torque with the driven gear (input shaft). Further, a separation mechanism is provided for separating the first rotation member and the second rotation member in the axial direction by a relative rotation speed of the second rotation member with respect to the first rotation member.
Therefore, the first rotation is performed only when the rotation speed of the driven gear (input shaft) and the rotation speed of the output shaft, for example, the rotation speed of the driven gear (input shaft) is larger than the rotation speed of the output shaft. The member and the second rotating member are separated from each other.

Therefore, in the invention described in claim 1,
A second rotating member that separates from the first rotating member is disposed so as to face a synchronizer ring that rotates the output shaft and the driven gear synchronously. for that reason,
As the second rotating member moves (separates), the synchronizer ring is pressed by the driven gear, and drag resistance acts on the driven gear.

[0012] According to the second aspect of the present invention, the second rotating member that separates the first rotating member from the first rotating member includes:
It is arranged to face the driven gear. for that reason,
By the movement of the second rotating member, a drag resistance is applied to the driven gear so as to be pressed.

Here, the gear rattling noise in a general gear transmission causes a problem when the input shaft and the output shaft are not connected, that is, when the engine is in an idling state and the gear is in a neutral state. That is, when the rotation speed of the input shaft is higher than the rotation speed of the output shaft. Therefore, when the rotation speed of the input shaft is higher than the rotation speed of the output shaft, the separation mechanism is configured so as to separate the first rotation member and the second rotation member, so that the gear toothing in the neutral state is performed. The generation of sound is prevented.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the invention described in claim 1 will be described based on a first embodiment shown in FIGS. This first
In the embodiment, for the convenience of explanation, for example, the invention described in claim 1 is adopted in a first gear of a gear transmission for performing five-speed shifting for a vehicle. In FIG. 1, this gear transmission includes a drive gear 21 that rotates integrally with an input shaft 20, a thrust bearing 23 on an output shaft 22 and a radially 1 rotatably fitted via the bearing portion 24
and a st gear 25.

On the other hand, a clutch hub 26 is connected to the output shaft 22.
Are spline-fitted, and a hub sleeve 27 is fitted to the outer peripheral portion of the clutch hub 26 so as to be movable only in the axial direction. A boss protruding toward the clutch hub 26 is formed on the first gear 25, and a spline piece 28 is spline-fitted to this boss.
The spline piece 28 has an outer peripheral portion with a spline that meshes with the hub sleeve 27, and has a tapered surface that becomes smaller in diameter as approaching the clutch hub 26. A synchronizer ring 29 configured to rotate integrally with the clutch hub 26 is loosely fitted on the outer peripheral side of the tapered surface.

A tapered surface corresponding to the tapered surface of the spline piece 28 is formed on the inner peripheral surface of the synchronizer ring 29. When the tapered surfaces approach while pressing, the spline piece 28 and the synchronizer ring 29, that is, the first gear 25 and the output shaft 22 which are engaged with the drive gear 21 and rotated.
Drag resistance is generated between the clutch gear 26 and the clutch hub 26 which rotates integrally with the first gear 25, and the first gear 25 and the output shaft 22 rotate synchronously.

Therefore, in the first embodiment, the output shaft 22
An annular clutch hub 26, which is spline-fitted with the clutch hub 26, is used as a first rotating member. In FIG. 2, the clutch hub 26 has keys 30 slidably mounted in an axial direction at a plurality of locations (for example, three locations at equal intervals) on the outer peripheral side thereof. Is pressed to the outer periphery (hub sleeve 27) side by a key spring 31 disposed at the center.

The portion of the clutch hub 26 where the key 30 and the key spring 31 are not disposed, the synchronizer ring 29 and the spline piece 28
And an annular second U-shaped cross section.
Of the rotating members 32 are loosely fitted. Specifically, one protruding portion of the second rotating member 32 having a substantially U-shaped cross section is disposed so as to be in axial contact with the synchronizer ring 29 and the other protruding portion has friction. Member 3
It is arranged so as to be opposed to the spline piece 28 in the radial direction through the intermediary 3 (see FIG. 3). That is, the second rotating member 33 is provided with a predetermined angle, that is, the key 30 and the key spring 31 of the clutch hub 26, independently of the clutch hub 26 and the synchronizer ring 29 that rotate integrally with the output shaft 22. The spline piece 28 should not interfere with the set part.
(The input shaft 20 and the first gear 25).

Only when the rotation speed of the input shaft 20 is greater than the rotation speed of the output shaft 22 is the space between the clutch hub 26 and the second rotating member 32 separated from the second rotating member 32 and the clutch hub 26. There is provided a separation mechanism for causing the separation. Specifically, the contact surface between the second rotating member 32 and the clutch hub 26 in the axial direction includes an inclined surface (hatched portion indicated by a dotted line) 34 inclined in the circumferential direction at a predetermined angle α. Flat surface (flat surface) 35
Are formed alternately, and the boundary between the inclined surface 34 and the flat surface 35 is constituted by a surface 36 (a surface parallel to the axial direction) perpendicular to the flat surface 35 (FIG. 4 and FIG. 4). 5).

The operation of the first embodiment will be described below. First, when the input shaft 20 is connected to the engine in the idling state via a clutch and the vehicle is stopped in a neutral state (see FIG. 4), the output shaft 2
2 and the clutch hub 26 and the synchronizer ring 29 are stopped, but the input shaft 20 and the first gear 2
5 and spline piece 28 are rotating. Here, since the friction member 33 is interposed between the spline piece 28 and the second rotating member 32, a small torque T1 is transmitted from the spline piece 28 to the second rotating member 32. The second rotating member 32 rotates so as to slide on the inclined surface 34 formed on the clutch hub 26 and the second rotating member 32 by the minute torque T1, so that the second rotating member 32 moves away from the clutch hub 26 in the axial direction. Go to The axial load F1 is given by the following equation.

F1 = T1 ・ (1-μs ・ tan α) /
rs · (μs + tan α) where μs: coefficient of friction of the inclined surface rs: equivalent radius of the inclined surface

The load F 1 for moving the second rotary member 32 in the axial direction is applied to the synchronizer ring 29.
Is pressed against the spline piece 28. This load F
1 is synchronizer ring 29 and spline piece 2
At the tapered surface 8, it is amplified by the drag resistance T 2 to prevent the rattling noise.

T2 = μg · rg · F1 / sin β where μg: coefficient of friction on the tapered surface rg: equivalent radius of the tapered surface β: taper angle

Next, a description will be given of the case of running the first gear. In this case, the rotation speed of the output shaft 22 (the clutch hub 26 and the synchronizer ring 29) and the input shaft 20 (1 s)
Since the rotation speeds of the t gear 25 and the second rotating member 32) are equal, no drag resistance is generated at any part.

Next, a description will be given of the case of running the second to fifth gears (see FIG. 5). In this case, the output shaft 22, the clutch hub 26, and the synchronizer ring 29 are rotating at a higher speed with respect to the input shaft 20, the first gear 25, and the spline piece 28. Therefore, the clutch hub 26 and the second rotating member 32 engage with each other on the vertical surface 36 and rotate integrally. At this time, the second
Rotating member 32 and spline piece 28 (1st gear 2
5, a small drag resistance T1 is generated between the input shaft 20 and the input shaft 20) through the friction member 33. However, since the drag resistance T1 is not amplified, it hardly affects the torque transmission efficiency. .

In the first embodiment, the clutch hub 2 is used as a first rotating member to reduce the rotating mass on the output shaft.
Although the first rotary member is used, the first rotary member only needs to rotate integrally with the output shaft. Therefore, the first rotary member can be formed separately from the clutch hub 26 as a matter of course. Also,
As the second rotating member 32 moves in the axial direction, the synchronizer ring 29 moves to the first gear 25 (spline piece 2).
8), an appropriate member may be disposed between the second rotating member 32 and the synchronizer ring 29 so as to indirectly press the synchronizer ring 29.

Next, the invention described in claim 2 will be described with reference to FIG.
A description will be given based on a second embodiment shown in FIG. In the second embodiment, as in the first embodiment described above, a driving gear 21 that rotates integrally with an input shaft 20, and a first gear that always meshes with the driving gear 21 and is rotatably supported by an output shaft 22. 25, a clutch hub 26 that rotates integrally with the output shaft 22, and a hub sleeve 2 that is movably engaged with the outer peripheral portion of the clutch hub 26 only in the axial direction.
7 and a synchronizer ring 29 that imparts drag resistance to the first gear 25 and the hub sleeve 27 as the hub sleeve 27 moves in the axial direction.

In the second embodiment, the first gear 2
The thrust bearing portion 23 supporting the shaft 5 on the output shaft 22 is constituted by a first rotating member 37 and a second rotating member 38. That is, the ring member that rotates integrally with the output shaft 22 via the ball member 39 fitted into the recess formed in the output shaft 22 is axially moved to the first rotation member 37 and the second rotation member 38. It is configured by dividing. Hereinafter, a specific description will be given.

The first rotating member 37 is formed in an annular shape, and has a concave portion provided on the inner peripheral side thereof for substantially fitting with the ball member 39. On the other hand, the second rotating member 3
8 is formed in an annular shape like the first rotating member 37,
A concave portion that fits with the ball member 39 is provided on the inner peripheral side. The concave portion of the second rotating member 38 is formed to be larger in the circumferential direction than the concave portion of the first rotating member 37. That is, the first rotating member 37 is configured to rotate integrally with the output shaft 22, while the second rotating member 38 is configured to be rotatable relative to the first rotating member within a predetermined range. (See FIG. 7).

The second rotating member 38 is disposed on the first gear 25 side, and the first rotating member 3
7 and the second rotating member 38 are arranged so as to abut on each other in the axial direction. Therefore, as in the first embodiment, the first
The separation mechanism between the rotating member 37 and the second rotating member 38 is
On these contact surfaces, an inclined surface 34 and a vertical surface 36 (a surface parallel to the axial direction) inclined in the circumferential direction at a predetermined angle α and a flat surface 35 in the circumferential direction are alternately formed. It is configured.

The outer peripheral portion of the second rotating member 38 is formed in a cylindrical shape so as to cover the outer peripheral portion of the first rotating member 37 (see FIG. 8). 1st
A friction member 33 is provided between the outer peripheral portion of the second rotating member 38 and the inner peripheral portion of the first gear 25 so that torque is transmitted to and from the gear 25.

The operation of the second embodiment will be described below. First, when the input shaft 20 is connected to the engine in an idling state via a clutch and the vehicle is stopped in a neutral state (see FIG. 9), the output shaft 2
2 is stopped, but the input shaft 20 and the first gear 25
Is spinning. In the second embodiment, a small torque T1 is transmitted between the second rotating member 38 and the first gear 25, and the second rotating member 38 comes into contact with the first rotating member 37 (the inclined surface 34). As in the first embodiment, an axial load F1 is generated, and the first rotating member 37 and the second rotating member 38 operate so as to be separated from each other.

In the second embodiment, the first rotating member 37
And the second rotating member 38 constitute the thrust bearing 23, and operate to reduce the axial clearance of the thrust bearing 23. Here, since the second rotating member and the clutch hub 26 are configured to face each other via the first gear 25, when the second rotating member 38 further moves, the first gear 25 is rotated by the second rotation. 1st between the member 38 and the clutch hub 26
The axial clearance of the gear 25 is also reduced. Therefore, the amplified drag resistance T3 acts on the contact surface between the first gear 25 and the second rotating member 38 and the contact surface between the first gear 25 and the clutch hub 26, and the clearance causing rattling is generated. Disappear.

T3 = μg · rg · F1 where μg: coefficient of friction on the tapered surface rg: equivalent radius of the tapered surface In running the first gear, the rotation speed of the output shaft 22 is equal to the rotation speed of the input shaft 20. Therefore, as in the first embodiment, no drag resistance is generated in any part. Also, during traveling of the second gear to the fifth gear (see FIG. 10), the first rotating member 37 and the second rotating member 38 are engaged with each other on the vertical surface 36 to rotate integrally, and rotate with the first gear 25. A small drag resistance T1 between the second rotating member 38 and the second rotating member 38;
As in the first embodiment, since the drag resistance T1 is not amplified, it hardly affects the torque transmission efficiency.

In the second embodiment, as in the first embodiment, in order to reduce the rotating mass of the output shaft 22, the thrust bearing 2
Although the first rotating member 37 and the second rotating member 38 are configured using the third ring member, the first rotating member and the second rotating member that are independent of the thrust bearing portion 23 are formed. Can be arranged. Also, the second rotating member 38
The second rotating member 38 indirectly presses the first gear 25 to apply the drag resistance because the first gear 25 may be configured to apply the drag resistance with the axial movement of the first gear 25. You can also.

The first embodiment and the second embodiment described above
When the hub sleeve 27 is moved in the axial direction, the key 30 moves together with the hub sleeve 27 in the axial direction as in the conventional gear transmission shown in FIG. It is pressed in the axial direction, and as a result, the tapered surface on the inner peripheral side thereof comes into contact with the corresponding tapered surface of the spline piece 28, and both start rotating synchronously. Then, the chamfer of the hub sleeve 27 and the chamfer of the synchronizer ring 29 come into contact with each other, and the hub sleeve 27 further moves in the axial direction. Finally, the spline is engaged, and the speed change operation is completed.

In the first embodiment and the second embodiment described above,
In the embodiment, when the driving force is interrupted when the input shaft 20 and the output shaft 22 are connected in the idling state, when the driving force is cut off by a so-called clutch, the rotational mass of the input shaft 20 and Due to the difference in the rotational mass of the output shaft 22 (usually, the rotational mass of the input shaft 20 <the rotational mass of the output shaft 22), the rotation of the output shaft 22 decreases first.
The drag resistance T2 is applied to the first gear 25, and the rotation speed of the input shaft 20 drops rapidly. Therefore, even if the reverse synchromesh mechanism is abolished, the reverse shift operation can be performed smoothly.

Further, in the first and second embodiments described above, the spline piece 28 or the spline piece 28 is provided on the first gear 25 depending on the relative rotation direction of the input shaft 20 with respect to the output shaft 22 for the sake of explanation. 1st gear 2
5, the drag resistance is applied to prevent the gear rattling noise, but, of course, all gears (2nd to 5t)
h) can be applied.

[0039]

As described above, according to the gear transmission of the present invention, only when the rotation speed of the input shaft is higher than the rotation speed of the output shaft, specifically, the prime mover is in the idling state and When the input shaft and the output shaft are not connected to each other, drag resistance is applied to the driven gear loosely fitted to the output shaft. Generation of rattling noise can be effectively prevented. In addition, when the driving force is cut off to the input shaft rotating in the idling state, specifically, when the clutch is operated to perform the reverse shift operation, the rotation speed of the input shaft is reduced. Since the reverse synchromesh mechanism is not required, and the structure of the transmission can be simplified, the configuration can be made extremely advantageous in terms of cost, reliability, and the like.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing one embodiment of the invention described in claim 1.

FIG. 2 is a sectional view taken along line II-II of FIG.

FIG. 3 is an enlarged view of a part III in FIG. 1;

FIG. 4 shows an input shaft rotation speed in the embodiment shown in FIG.
It is a schematic diagram which shows the operation | movement of a 1st rotating member (clutch hub) and a 2nd rotating member in the case of an output shaft rotation speed.

FIG. 5 shows an output shaft rotation speed in the embodiment shown in FIG.
It is a schematic diagram which shows the operation | movement of a 1st rotating member and a 2nd rotating member in the case of an input shaft rotation speed.

FIG. 6 is a schematic sectional view showing one embodiment of the invention described in claim 2;

FIG. 7 is a sectional view taken along line VII-VII of FIG. 6;

FIG. 8 is a diagram schematically showing the side surface of FIG. 7;

FIG. 9 shows the input shaft rotation speed in the embodiment shown in FIG.
It is a schematic diagram which shows operation | movement of a 1st rotating member and a 2nd rotating member in the case of an output shaft rotation speed.

FIG. 10 is a schematic diagram showing the operation of a first rotating member and a second rotating member when the output shaft rotation speed> the input shaft rotation speed in the embodiment shown in FIG. 6;

FIG. 11 is a schematic sectional view showing an example of a conventional gear transmission.

[Explanation of symbols]

REFERENCE SIGNS LIST 20 input shaft 22 output shaft 25 1st gear (driven gear) 26 clutch hub (first rotating member but in first embodiment) 32 second rotating member (but in first embodiment) 33 friction member 34 inclined surface 36 vertical Surface (plane parallel to output shaft) 37 First rotating member (second embodiment) 38 Second rotating member (second embodiment)

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-5-39815 (JP, A) JP-A-6-288461 (JP, A) JP-A-6-117449 (JP, A) 73519 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) F16D 23/04-23/06 F16H 57/12

Claims (2)

(57) [Claims] A drive gear that rotates integrally with the input shaft, a driven gear that always meshes with the drive gear and is rotatably supported on the output shaft, a clutch hub that rotates integrally with the output shaft, A hub sleeve movably engaged in the axial direction with an outer peripheral portion of the clutch hub, and a drag resistance is applied to the hub sleeve and the driven gear as the hub sleeve moves in the axial direction, so that the hub sleeve and the driven gear are synchronously rotated. A first rotating member that rotates integrally with the output shaft, and is supported by the output shaft so as to be rotatable relative to the first rotating member by a predetermined angle. A second rotating member is disposed so as to face the output shaft, and a friction transmission unit for transmitting torque between the driven gear and the second rotating member is provided; A separating mechanism that is operated by relative rotation of the second rotating member with respect to the first rotating member in a predetermined one direction to separate the first rotating member and the second rotating member from each other in an axial direction; Is provided between the first rotating member and the second rotating member, and the second rotating member and the synchronizer ring are arranged to face each other on the output shaft. Gear transmission. 2. A drive gear that rotates integrally with the input shaft, a driven gear that always meshes with the drive gear and is rotatably supported on the output shaft, and a clutch hub that rotates integrally with the output shaft. A hub sleeve movably engaged in the axial direction with an outer peripheral portion of the clutch hub, and a drag resistance is applied to the hub sleeve and the driven gear as the hub sleeve moves in the axial direction, so that the hub sleeve and the driven gear are synchronously rotated. A first rotating member that rotates integrally with the output shaft, and is supported by the output shaft so as to be rotatable relative to the first rotating member by a predetermined angle. A second rotating member is disposed so as to face the output shaft, and a friction transmission unit for transmitting torque between the driven gear and the second rotating member is provided; A separating mechanism that is operated by relative rotation of the second rotating member with respect to the first rotating member in a predetermined one direction to separate the first rotating member and the second rotating member from each other in an axial direction; Is provided between the first rotating member and the second rotating member, and the second rotating member and the driven gear are disposed to face each other on the output shaft. Gear transmission.